/**
 * 可伸缩布局
 * rem计算方式：设计图尺寸px / 100 = 实际rem  例: 100px = 1rem
 */
export default {
  layout () {
    (function (window) {
      /* 设计图文档宽度 */
      const docWidth = 750
      const doc = window.document
      const docEl = doc.documentElement
      let resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'

      let recalc = (function refreshRem () {
        let clientWidth = docEl.getBoundingClientRect().width

        /* 8.55：小于320px不再缩小，11.2：大于420px不再放大 */
        docEl.style.fontSize = Math.max(Math.min(20 * (clientWidth / docWidth), 11.2), 8.55) * 5 + 'px'

        return refreshRem
      })()

      /* 添加倍屏标识，安卓倍屏为1 */
      docEl.setAttribute('data-dpr', window.navigator.appVersion.match(/iphone/gi) ? window.devicePixelRatio : 1)

      if (/iP(hone|od|ad)/.test(window.navigator.userAgent)) {
        /* 添加IOS标识 */
        doc.documentElement.classList.add('ios')
        /* IOS8以上给html添加hairline样式，以便特殊处理 */
        if (parseInt(window.navigator.appVersion.match(/OS (\d+)_(\d+)_?(\d+)?/)[1], 10) >= 8) {
          doc.documentElement.classList.add('hairline')
        }
      }

      if (!doc.addEventListener) return
      window.addEventListener(resizeEvt, recalc, false)
      doc.addEventListener('DOMContentLoaded', recalc, false)
    })(window)
  }
}
